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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old February 25th, 2016, 12:12 AM
bobdylan bobdylan is offline
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Default Removing stuck pistons

Looking for proven techniques for removing pistons, one thing taht sounds good is, after soaking with? pack cylinder with grease, put a head that valves seal tight. modify spark plug and instal grease zerk, use pressure from grease gun to shve piston out. Has anyone tried this? Bob
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Old February 25th, 2016, 04:12 PM
George Bongert George Bongert is offline
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Default Re: Removing stuck pistons

Quote:
Originally Posted by bobdylan View Post
Looking for proven techniques for removing pistons, one thing taht sounds good is, after soaking with? pack cylinder with grease, put a head that valves seal tight. modify spark plug and instal grease zerk, use pressure from grease gun to shve piston out. Has anyone tried this? Bob
Greetings Bob!

I have heard of the grease gun method, although I've never tried it myself. As to soaking the cylinder(s), a friend of mine recommends a 50/50 mixture of laquer thinner and brake fluid to break the bond between the rusted cylinder and piston. Again, I never tried it myself, but he claims it works well. If you try it, let the rest of us know whether it works or not.
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Old February 25th, 2016, 04:19 PM
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Default Re: Removing stuck pistons

An old mechanic once told me, water is what stuck it, so it will work the best to unstick it. I found a product called evaporust. It is water based, and it eats rust like you would not believe. It may take a few days or weeks, but i think it will work.
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Old February 25th, 2016, 04:29 PM
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Default Re: Removing stuck pistons

I don't know anything, but can you just put a block of wood on them and use a BFH to pound them out?


Maybe putting a jack under them will push them out the top?
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Old February 26th, 2016, 03:57 PM
abus319 abus319 is offline
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Default Re: Removing stuck pistons

+1 for evaporust assuming its the rings that are stuck and your goal is to salvage the pistons.
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Old February 26th, 2016, 05:26 PM
bobdylan bobdylan is offline
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Default Re: Removing stuck pistons

Thanks, have you tried this? Bob
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Old February 26th, 2016, 10:57 PM
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Default Re: Removing stuck pistons

Haven't tried it on pistons. I have a pistol that my uncle found when plowing about 50 years ago. I think it dates back to the late 1800 era. Tried soaking it in diesel fuel for 2 years, did no good. I put the pistol in a bucket of evaporust and soaked it for a couple months. I was then able to rock the cylinder a little bit. I was pretty excited about that. So put it back in bucket, but did not get back to it for a couple months. Wheni pulled it out another chemical reaction occured, and a white powder had formed on it. Pistol stuck again. What a bummer. So dont leave evaporust in too long.
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Old February 27th, 2016, 01:13 AM
bobdylan bobdylan is offline
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Default Re: Removing stuck pistons

I think on a small part I would use electrolosis, using a bucket, battery charger some rebar. There some on youtube, I keep thinking I am going to try it, but there is the twenty unfinished projects.
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Old February 27th, 2016, 01:24 AM
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Default Re: Removing stuck pistons

Quote:
Originally Posted by bobdylan View Post
Looking for proven techniques for removing pistons, one thing taht sounds good is, after soaking with? pack cylinder with grease, put a head that valves seal tight. modify spark plug and instal grease zerk, use pressure from grease gun to shve piston out. Has anyone tried this? Bob
The grease method sounds like a pretty good idea, it sure works slick for pressed in pilot bearings. The first pic below is a couple different rust breaker sprays I've had good luck with before. I've heard kerosene and ATF mix works well but never tried it.

Quote:
Originally Posted by ilvracn View Post
Haven't tried it on pistons. I have a pistol that my uncle found when plowing about 50 years ago. I think it dates back to the late 1800 era. Tried soaking it in diesel fuel for 2 years, did no good. I put the pistol in a bucket of evaporust and soaked it for a couple months. I was then able to rock the cylinder a little bit. I was pretty excited about that. So put it back in bucket, but did not get back to it for a couple months. Wheni pulled it out another chemical reaction occured, and a white powder had formed on it. Pistol stuck again. What a bummer. So dont leave evaporust in too long.

Cool find! I wish I could remember how Mom de-rusted this pistol about 45 years ago but it came out well. I remember she soaked it in something for quite a while in our utility room and I don't remember it having a bad smell or anything. She found it while digging for old bottles at a long-gone railroad station, and it is also from around the same era.

Sorry about the brief hi-jack!

DAC
Attached Images
File Type: jpg rust 002.jpg (1.20 MB, Multiple views, 5 clicks)
File Type: jpg rust 004.jpg (1.36 MB, Multiple views, 6 clicks)
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Old February 27th, 2016, 01:44 PM
abus319 abus319 is offline
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Default Re: Removing stuck pistons

I haven't tried the evaporust on a stuck piston yet. My thoughts were that eliminating the rust bond between the rings and the cylinder wall with a non damaging product like evaporust might be a better first step than applying force.
I know these pistons are stout but i would be concerned about breaking or deforming a ring land with the grease gun method.
On my 478 I used a mix of trans fluid and diesel in the cal, and built a torque plate to attach an impact to the end of the crank. Two or three second burst, reversing each time, several times a day broke it loose.
Do you have the heads off, or is this one of the engines that was stored without the heads? if so how do they look?

Last edited by abus319; February 27th, 2016 at 03:35 PM.
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